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Senescence is a multifaceted and dynamic developmental phase pivotal in the plant's lifecycle, exerting significant influence and involving intricate regulatory mechanisms marked by a variety of structural, biochemical and molecular alterations. Biochemical changes, including reactive oxygen species (ROS) generation, membrane deterioration, nucleic acid degradation and protein degradation, characterize flower senescence. The progression of senescence entails a meticulously orchestrated network of interconnected molecular mechanisms and signalling pathways, ensuring its synchronized and efficient execution. Within flowering plants, petal senescence emerges as a crucial aspect significantly impacting flower longevity and postharvest quality, emphasizing the pressing necessity of unravelling the underlying signalling cascades orchestrating this process. Understanding the complex signalling pathways regulating petal senescence holds paramount importance, not only shedding light on the broader phenomenon of plant senescence but also paving the way for the development of targeted strategies to enhance the postharvest longevity of cut flowers. Various signalling pathways participate in petal senescence, encompassing hormone signalling, calcium signalling, protein kinase signalling and ROS signalling. Among these, the ethylene signalling pathway is extensively studied, and the manipulation of genes associated with ethylene biosynthesis or signal transduction has demonstrated the potential to enhance flower longevity. A thorough understanding of these complex pathways is critical for effectively delaying flower senescence, thereby enhancing postharvest quality and ornamental value. Therefore, this review adopts a viewpoint that combines fundamental research into the molecular intricacies of senescence with a practical orientation towards developing strategies for improving the postharvest quality of cut flowers. The innovation of this review is to shed light on the pivotal signalling cascades underpinning flower senescence and offer insights into potential approaches for modulating these pathways to postpone petal senescence in ornamental plants.Key message: Senescence in flowering plants, particularly petal senescence, plays a central role in their life cycle. Unravelling the intricate signalling networks involved in this process is crucial for enhancing flower postharvest quality. This review highlights the significance of understanding these signalling cascades to develop strategies for delaying petal senescence and improving postharvest longevity. [ABSTRACT FROM AUTHOR]

WRKY transcription factors play a central role in controlling plant organ senescence; however, it is unclear whether and how they regulate petal senescence in the widely grown ornamental plant tulip (Tulipa gesneriana). In this study, we report that TgWRKY75 promotes petal senescence by enhancing the synthesis of both abscisic acid (ABA) and salicylic acid (SA) in tulip and in transgenic Arabidopsis. The expression level of TgWRKY75 was up-regulated in senescent petals, and exogenous ABA or SA treatment induced its expression. The endogenous contents of ABA and SA significantly increased during petal senescence and in response to TgWRKY75 overexpression. Two SA synthesis-related genes, TgICS1 and TgPAL1 , were identified as direct targets of TgWRKY75, which binds to their promoters. In parallel, TgWRKY75 activated the expression of the ABA biosynthesis-related gene TgNCED3 via directly binding to its promoter region. Site mutation of the W-box core motif located in the promoters of TgICS1 , TgPAL1 , and TgNCED3 eliminated their interactions with TgWRKY75. In summary, our study demonstrates a dual regulation of ABA and SA biosynthesis by TgWRKY75, revealing a synergistic process of tulip petal senescence through feedback regulation between TgWRKY75 and the accumulation of ABA and SA. [ABSTRACT FROM AUTHOR]

Carnation (Dianthus caryophyllus L.) is a typical ethylene-sensitive cut flower. Variations in carnation vase life and sensitivity to ethylene have been reported, but no detailed analysis has been performed to date. In order to investigate the ethylene sensitivity of different cut carnation varieties and study the effect of ethylene on postharvest physiological changes of different carnation varieties, 14 varieties were used to explore ethylene sensitivity, and six varieties were used to analyze the release pattern of endogenous ethylene and the expression pattern of related genes. The results showed that among the 14 carnation varieties, 'Master' had the strongest ethylene sensitivity and 'Snow White' had the weakest ethylene sensitivity. Ethylene release changes of 'Master' are the terminal ascending type, and 'Cloud Shium', 'Little Pink', 'Seashell', 'Freedom' and 'Snow White' are the similar ethylene leap type. Ethylene biosynthesis genes DcACS1 and DcACO1 of 'Master' were up-regulated the most, and DcACO1 of 'Snow White' was the least up-regulated. The transient silencing and overexpression of DcACS1 and DcACO1 were performed and it was found that transient silencing can significantly delay aging, and overexpression significantly accelerates aging. This study laid the foundation for further research on the molecular mechanism of ethylene regulation of postharvest senescence of cut flowers of carnation, and also indicated the direction for further breeding and artificial screening of new storage tolerant carnation species by gene editing technology.

Flowers are crucial for the reproduction of flowering plants and their senescence has drastic effects on plant-animal interactions as well as pollination. Petal senescence is the final phase of flower development which is regulated by hormones and genes. Among these, jasmonic acid (JA) has emerged as a major contributor to petal senescence, but its molecular mechanisms remain elusive. Here, the role of JA in petal senescence in Arabidopsis was investigated. We showed that petal senescence in aos mutant was significantly delayed, which also affected petal cell size and proliferation. Similar significant delays in petal senescence were observed in dad1 and coi1 mutants. However, MYB21/24 and MYC2/3/4, known downstream regulators of JA in flower development, played no role in petal senescence. This indicated that JA regulates petal senescence by modulating other unknown transcription factors. Transcriptomic analysis revealed that AOS altered the expression of 3681 genes associated, and identified groups of differentially expressed transcription factors, highlighting the potential involvement of AP-2, WRKY and NAC. Furthermore, bHLH13, bHLH17 and URH2 were identified as potential new regulators of JA-mediated petal senescence. In conclusion, our findings suggest a novel genetic pathway through which JA regulates petal senescence in Arabidopsis. This pathway operates independently of stamen development and leaf senescence, suggesting the evolution of specialized mechanisms for petal senescence. [ABSTRACT FROM AUTHOR]

Summary: Petal senescence is the final stage of flower development. Transcriptional regulation plays key roles in this process. However, whether and how post‐transcriptional regulation involved is still largely unknown. Here, we identified an ethylene‐induced NAC family transcription factor DcNAP in carnation (Dianthus caryophyllus L.). One allele, DcNAP‐dTdic1, has an insertion of a dTdic1 transposon in its second exon. The dTdic1 transposon disrupts the structure of DcNAP and causes alternative splicing, which transcribes multiple domain‐deleted variants (DcNAP2 and others). Conversely, the wild type allele DcNAP transcribes DcNAP1 encoding an intact NAC domain. Silencing DcNAP1 delays and overexpressing DcNAP1 accelerates petal senescence in carnation, while silencing and overexpressing DcNAP2 have the opposite effects, respectively. Further, DcNAP2 could interact with DcNAP1 and interfere the binding and activation activity of DcNAP1 to the promoters of its downstream target ethylene biosynthesis genes DcACS1 and DcACO1. Lastly, ethylene signalling core transcriptional factor DcEIL3‐1 can activate the expression of DcNAP1 and DcNAP2 in the same way by binding their promoters. In summary, we discovered a novel mechanism by which DcNAP regulates carnation petal senescence at the post‐transcriptional level. It may also provide a useful strategy to manipulate the NAC domains of NAC transcription factors for crop genetic improvement. [ABSTRACT FROM AUTHOR]

Carnation (Dianthus caryophyllus L.) is a typical ethylene-sensitive cut flower, but a few differences in ethylene sensitivity have been reported for different potted carnation species. In this study, we investigated the relationship between vase life, ethylene sensitivity, ethylene biosynthesis gene expression, and flower volatile substance content of 17 different potted carnation varieties. It was found that under the same post-harvest environmental conditions, the vase life of different varieties ranged from 6.2−14.2 d. Among the 17 varieties, 'Cherry' and 'Grace Bay' were highly sensitive to ethylene, and qRT-PCR analysis showed that their ethylene biosynthesis genes DcACS1 and DcACO1 expression increased the most, while 'Pink and Purple', 'Bondi Beach', and 'Grane Beach' showed the opposite pattern. In addition, the lower ethylene release was important in leading to longer vase life of potted carnations, and that ethylene release from shorter vase life varieties was 2.5−4.5 times greater than that of longer vase life varieties. Varieties that are more sensitive to ethylene are more likely to have a shorter vase life due to early disruption of water relations, which is mainly the result of reduced stem hydraulic conductivity and transpiration water loss. Analysis of volatile substances showed that ethylene had no significant effect on the release of volatile substances from potted carnations. Therefore, a better understanding of petal senescence in potted carnations will help us to improve measures to extend flower longevity according to the ethylene sensitivity of different varieties.

SUMMARY: Carnation (Dianthus caryophyllus L.) is a respiratory climacteric flower, comprising one of the most important cut flowers that is extremely sensitive to plant hormone ethylene. Ethylene signaling core transcription factor DcEIL3‐1 plays a key role in ethylene induced petal senescence in carnation. However, how the dose of DcEIL3‐1 is regulated in the carnation petal senescence process is still not clear. Here, we screened out two EBF (EIN3 Binding F‐box) genes, DcEBF1 and DcEBF2, which showed quick elevation by ethylene treatment according to the ethylene induced carnation petal senescence transcriptome. Silencing of DcEBF1 and DcEBF2 accelerated, whereas overexpression of DcEBF1 and DcEBF2 delayed, ethylene induced petal senescence in carnation by influencing DcEIL3‐1 downstream target genes but not DcEIL3‐1 itself. Furthermore, DcEBF1 and DcEBF2 interact with DcEIL3‐1 to degrade DcEIL3‐1 via an ubiquitination pathway in vitro and in vivo. Finally, DcEIL3‐1 binds to the promoter regions of DcEBF1 and DcEBF2 to activate their expression. In conclusion, the present study reveals the mutual regulation between DcEBF1/2 and DcEIL3‐1 during ethylene induced petal senescence in carnation, which not only expands our understanding about ethylene signal regulation network in the carnation petal senescence process, but also provides potential targets with respect to breeding a cultivar of long‐lived cut carnation. Significance Statement: Carnation is a typical ethylene sensitive cut flower worldwide and DcEIL3‐1 transcription factor plays important role in ethylene induced petal senescence in carnation. However, how ethylene regulates DcEIL3‐1 itself remains largely unknown. We found that there is a mutual regulation between DcEBF1/2 and DcEIL3‐1 at the transcriptional and post‐translational levels, which indicates that the negative feedback regulation loop plays a key role in regulating the petal senescence process. [ABSTRACT FROM AUTHOR]

One of the classes of the plant developmental programmed cell death (PCD) is vacuolar cell death or autolysis. The results of the transmission electron microscope (TEM) studies indicated that this type of PCD occurs during the petal senescence of Antirrhinum majus "Legend White" flowers. The major hallmarks of the process related to the ultrastructure of the cells involved chloroplast degradation, vacuolation, chromatin condensation, cell wall swelling, degradation of Golgi apparatus, protoplasmic shrinkage, degradation of the endoplasmic reticulum, nuclear fragmentation, rupture of tonoplast, and plasma membrane. Macroautophagy and microautophagy processes were also clearly observed during vacuole formation. As in yeasts, in the present study, Golgi apparatus became autophagosome-like structures during degradation that had autophagy activity and then disappeared. Our results revealed a type of selective microautophagy, piecemeal microautophagy of the nucleus (PMN), in nuclear degradation during PCD of petals that has not previously been reported in plants. Moreover, vesicular structures, such as paramural and multilamellar bodies, were observed in some stages. [ABSTRACT FROM AUTHOR]

SUMMARY: Carnation (Dianthus caryophyllus L.) is one of the most famous and ethylene‐sensitive cut flowers worldwide, but how ethylene interacts with other plant hormones and factors to regulate petal senescence in carnation is largely unknown. Here we found that a gene encoding WRKY family transcription factor, DcWRKY33, was significantly upregulated upon ethylene treatment. Silencing and overexpression of DcWRKY33 could delay and accelerate the senescence of carnation petals, respectively. Abscisic acid (ABA) and H2O2 treatments could also accelerate the senescence of carnation petals by inducing the expression of DcWRKY33. Further, DcWRKY33 can bind directly to the promoters of ethylene biosynthesis genes (DcACS1 and DcACO1), ABA biosynthesis genes (DcNCED2 and DcNCED5), and the reactive oxygen species (ROS) generation gene DcRBOHB to activate their expression. Lastly, relationships are existed between ethylene, ABA and ROS. This study elucidated that DcWRKY33 promotes petal senescence by activating genes involved in the biosynthesis of ethylene and ABA and accumulation of ROS in carnation, supporting the development of new strategies to prolong the vase life of cut carnation. Significance Statement: Carnation is a well‐known ethylene‐sensitive cut flower. How ethylene interacts with other factors to influence petal senescence in carnation remains largely unknown. We found that DcWRKY33 can integrate ethylene biosynthesis, abscisic acid biosynthesis, and reactive oxygen species generation pathways to regulate petal senescence in carnation. The tripartite amplification loop plays an important role in regulating petal senescence. [ABSTRACT FROM AUTHOR]

Although numerous transcription factors with antagonistic activities have been shown to contribute to growth and development, whether and how they regulate senescence in plants is largely unknown. In this study, we investigated the role of antagonistic transcription factors in petal senescence in carnation (Dianthus caryophyllus), one of the most common types of ethylene-sensitive cut flowers produced worldwide. We identified DcHB30 that encodes a ZF-HD transcription factor that is down-regulated in ethylene-treated petal transcriptomes. We found that silencing DcHB30 accelerated ethylene-induced petal senescence and that DcHB30 physically interacts with DcWRKY75, a positive regulator of ethylene-induced petal senescence. Phenotypic characterization and molecular evidence indicated that DcHB30 and DcWRKY75 competitively regulate the expression of their co-targeted genes DcACS1 , DcACO1 , DcSAG12 , and DcSAG29 by reciprocally inhibiting the DNA-binding activity of each other on the gene promoters. This transcriptional regulation mechanism demonstrates that these transcription factors serve as positive and negative regulators in ethylene-induced petal senescence in carnation. Thus, our study provides insights into how antagonizing transcription factors regulate plant senescence. [ABSTRACT FROM AUTHOR]

We investigated whether ethylene is involved in the stem-bending mechanism of the two different gerberas [long-lived cultivar 'Mary Queen' and short-lived cultivar 'Harmony'] by pretreating the stems with an ethylene-releasing compound (Ethephon), an ethylene-action inhibitor [silver thiosulfate (STS)], or Ethephon in combination with STS (Ethephon + STS), using distilled water as the control. In the cv. 'Mary Queen,' the control stems did not show stem bending, while the treatment groups showed bending at 6 and 9 days after treatment (DAT). In the cv. 'Harmony,' the bending rate observed in the Ethephon-treated stems was lower than the other treatments at 9 DAT. However, a lower bending rate in the Ethephon group relative to the other treatments is unlikely to be associated with ethylene action, because the bending rate observed in the Ethephon + STS group was significantly higher than the STS group. In addition, the bending rates of both cultivars were not associated with lignin contents or the expression of lignin biosynthesis genes in the stems. As it is complicated to conclude the role of Ethephon in stem bending of the gerberas, these results suggest that the use of Ethephon to delay stem bending in cut gerberas is not warranted. [ABSTRACT FROM AUTHOR]

Metacaspases are structural homologs of the metazoan caspases that are found in plants, fungi, and protozoans. They are cysteine proteases that function during programmed cell death, stress, and cell proliferation. A putative metacaspase designated PhMC2 was cloned from Petunia × hybrida, and sequence alignment and phylogenetic analysis revealed that it encodes a type II metacaspase. PhMC2 cleaved protease substrates with an arginine residue at the P1 site and cysteine (iodoacetamide) and arginal (leupeptin) protease inhibitors nearly abolished this activity. The activity of PhMC2 was highest at pH 8, and the putative catalytic site cysteine residue was required for optimal activity. Quantitative PCR showed that PhMC2 transcripts were detectable in petunia corollas, styles, and ovaries. Expression patterns were not upregulated during petal senescence but were higher at the middle stages of development when flower corollas were fully open but not yet starting to wilt. PhMC1, a type I metacaspase previously identified in petunia, and PhMC2 were differentially regulated in vegetative tissues in response to biotic and abiotic stresses. PhMC2 expression was upregulated to a greater extent than PhMC1 following Botrytis cinerea infection, while PhMC1 was upregulated more by drought, salinity, and low nutrient stress. These results suggest that petunia metacaspases are involved in flower development, senescence, and stress responses. [ABSTRACT FROM AUTHOR]

Abstract Background This study investigated the effects of ethylene release compounds (ethephon), ethylene-action inhibitors (silver thiosulfate: STS), and nitric oxide donor (sodium nitroprusside: SNP) on stem bending of snapdragon flowers. Moreover, the effects of plant growth supplements [6-benzyladenine (BA), gibberellic acid 3 (GA3), and calcium chloride (CaCl2)] on the stem bending were also extensively investigated. Results Ethephon completely prevented stem bending until 9 days after treatment (9 DAT). STS exhibited the highest bending rate, while SNP did not significantly affect the bending compared to the controls. The bending results were associated with the results of stem curvature, relative shoot elongation, ethylene production, and lignin content, that are involved in the stem bending mechanism. This was proven by the expression analysis of genes involved in ethylene and lignin biosynthetic pathways. The addition of plant growth supplements slightly or significantly delayed stem bending in the treatments (control, SNP, and STS) and significantly reduced petal senescence in ethephon at 9 DAT. Conclusion These results show the preventive role of ethephon in the stem bending of cut snapdragon. Moreover, the combination of ethephon with supplements also provided information that could guide the development of strategies to delay stem bending in other cut flowers that undergo serious bending during a short vase life.

Developmental petal senescence is a type of programmed cell death (PCD), during which the production of ethylene is induced, the expression of PCD-related genes is upregulated, and nutrients are recycled. Autophagy is an intracellular mechanism involved in PCD modulation and nutrient cycling. As a central component of the autophagy pathway, Autophagy Gene 6 (ATG6) was previously shown as a negative regulator of petal senescence. To better understand the role of autophagy in ethylene biosynthesis and nutrient remobilization during petal senescence, we generated and characterized the knockout (KO) mutants of PhATG6 using CRISPR/Cas9 in Petunia × hybrida 'Mitchell Diploid.' PhATG6- KO lines exhibited decreased flower longevity when compared to the flowers of the wild-type or a non-mutated regenerative line (controls), confirming the negative regulatory role of ATG6 in petal senescence. Smaller capsules and fewer seeds per capsule were produced in the KO plants, indicating the crucial function of autophagy in seed production. Ethylene production and ethylene biosynthesis genes were upregulated earlier in the KO lines than the controls, indicating that autophagy affects flower longevity through ethylene. The transcript levels of petal PCD-related genes, including PhATG6 , PhATG8d , PhPI3K (Phosphatidylinositol 3-Kinase), and a metacaspase gene PhMC1 , were upregulated earlier in the corollas of PhATG6- KO lines, which supported the accelerated PCD in the KO plants. The remobilization of phosphorus was reduced in the KO lines, showing that nutrient recycling was compromised. Our study demonstrated the important role of autophagy in flower lifespan and seed production and supported the interactions between autophagy and various regulatory factors during developmental petal senescence. [ABSTRACT FROM AUTHOR]

Developmental petal senescence is a type of programmed cell death (PCD), during which the production of ethylene is induced, the expression of PCD-related genes is upregulated, and nutrients are recycled. Autophagy is an intracellular mechanism involved in PCD modulation and nutrient cycling. As a central component of the autophagy pathway, Autophagy Gene 6 (ATG6) was previously shown as a negative regulator of petal senescence. To better understand the role of autophagy in ethylene biosynthesis and nutrient remobilization during petal senescence, we generated and characterized the knockout (KO) mutants of PhATG6 using CRISPR/Cas9 in Petunia × hybrida ‘Mitchell Diploid.’ PhATG6-KO lines exhibited decreased flower longevity when compared to the flowers of the wild-type or a non-mutated regenerative line (controls), confirming the negative regulatory role of ATG6 in petal senescence. Smaller capsules and fewer seeds per capsule were produced in the KO plants, indicating the crucial function of autophagy in seed production. Ethylene production and ethylene biosynthesis genes were upregulated earlier in the KO lines than the controls, indicating that autophagy affects flower longevity through ethylene. The transcript levels of petal PCD-related genes, including PhATG6, PhATG8d, PhPI3K (Phosphatidylinositol 3-Kinase), and a metacaspase gene PhMC1, were upregulated earlier in the corollas of PhATG6-KO lines, which supported the accelerated PCD in the KO plants. The remobilization of phosphorus was reduced in the KO lines, showing that nutrient recycling was compromised. Our study demonstrated the important role of autophagy in flower lifespan and seed production and supported the interactions between autophagy and various regulatory factors during developmental petal senescence.

Background: This study investigated the effects of ethylene release compounds (ethephon), ethylene-action inhibitors (silver thiosulfate: STS), and nitric oxide donor (sodium nitroprusside: SNP) on stem bending of snapdragon flowers. Moreover, the effects of plant growth supplements [6-benzyladenine (BA), gibberellic acid 3 (GA3), and calcium chloride (CaCl2)] on the stem bending were also extensively investigated. Results: Ethephon completely prevented stem bending until 9 days after treatment (9 DAT). STS exhibited the highest bending rate, while SNP did not significantly affect the bending compared to the controls. The bending results were associated with the results of stem curvature, relative shoot elongation, ethylene production, and lignin content, that are involved in the stem bending mechanism. This was proven by the expression analysis of genes involved in ethylene and lignin biosynthetic pathways. The addition of plant growth supplements slightly or significantly delayed stem bending in the treatments (control, SNP, and STS) and significantly reduced petal senescence in ethephon at 9 DAT. Conclusion: These results show the preventive role of ethephon in the stem bending of cut snapdragon. Moreover, the combination of ethephon with supplements also provided information that could guide the development of strategies to delay stem bending in other cut flowers that undergo serious bending during a short vase life. [ABSTRACT FROM AUTHOR]

Main conclusion: Numerous transcription factor genes and methylation-related genes were differentially expressed in senescent petals compared with control petals. Studying petal senescence is crucial for extending the postharvest longevity of cut flowers, but petal senescence remains relatively unexplored compared to well-studied leaf senescence. In this study, a combined transcriptomic and proteomic analysis of senescent (22 days after cutting) and control (0 day after cutting) petals was performed to investigate the molecular processes underlying petal senescence of chrysanthemum (Chrysanthemum morifolium Ramat.), an important cut flower crop worldwide. A total of 11,324 differentially expressed genes (DEGs), including 4888 up-regulated and 6436 down-regulated genes, and 403 differentially expressed proteins (DEPs), including 210 up-regulated and 193 down-regulated proteins, were identified at transcript and protein levels, respectively. A cross-comparison of transcriptomic and proteomic data identified 257 consistent DEGs/DEPs, including 122 up-regulated and 135 down-regulated DEGs/DEPs. Kyoto encyclopedia of genes and genomes (KEGG) enrichment analysis showed that “cutin, suberine and wax biosynthesis” is a main pathway for both DEGs and DEPs, especially for down-regulated DEGs/DEPs. Functional analysis indicated that chrysanthemum genes mainly encoding putative cytochrome P450s, non-specific lipid-transfer proteins, subtilisin-like proteases, AAA-ATPases, proteins essential for cuticular wax biosynthesis, and proteins in hormone signal transduction or ubiquitination were differentially expressed at both transcript and protein levels. In addition, numerous transcription factor genes and methylation-related genes were also differentially expressed, inferring an involvement of transcriptional and epigenetic regulation in petal senescence. These results provide a valuable resource of studying chrysanthemum senescence and significant insights into petal senescence. [ABSTRACT FROM AUTHOR]

SUMMARY: Carnation (Dianthus caryophyllus L.) is one of the most important and typical ethylene sensitive cut flowers worldwide, although how ethylene influences the petal senescence process in carnation remains largely unknown. Here, we screened out one of the key transcription factors, DcWRKY75, using a constructed ethylene induced petal senescence transcriptome in carnation and found that it shows quick induction by ethylene treatment. Silencing of DcWRKY75 delays ethylene induced petal senescence in carnation. Molecular evidence confirms that DcWRKY75 can bind to the promoter regions of two main ethylene biosynthetic genes (DcACS1 and DcACO1) and a couple of senescence associated genes (DcSAG12 and DcSAG29) to activate their expression. Furthermore, we show that DcWRKY75 is a direct target gene of DcEIL3‐1, which is a homolog of the ethylene signaling core transcription factor EIN3 in Arabidopsis. DcEIL3‐1 can physically interact with DcWRKY75 and silencing of DcEIL3‐1 also delays ethylene induced petal senescence in carnation and inhibits the ethylene induced expression of DcWRKY75 and its target genes. The present study demonstrates that the transcriptional regulation network is vitally important for ethylene induced petal senescence process in carnation and potentially in other ethylene sensitive cut flowers. Significance Statement: Carnation is one of the most important and typical ethylene sensitive cut flowers worldwide, although how ethylene influences the petal senescence process in carnation remains largely unknown. We found that DcWRKY75 promotes ethylene induced petal senescence in carnation, which means that the transcriptional regulation networks play important roles in regulating the petal senescence process. [ABSTRACT FROM AUTHOR]

Metacaspases are structural homologs of the metazoan caspases that are found in plants, fungi, and protozoans. They are cysteine proteases that function during programmed cell death, stress, and cell proliferation. A putative metacaspase designated PhMC2 was cloned from Petunia × hybrida, and sequence alignment and phylogenetic analysis revealed that it encodes a type II metacaspase. PhMC2 cleaved protease substrates with an arginine residue at the P1 site and cysteine (iodoacetamide) and arginal (leupeptin) protease inhibitors nearly abolished this activity. The activity of PhMC2 was highest at pH 8, and the putative catalytic site cysteine residue was required for optimal activity. Quantitative PCR showed that PhMC2 transcripts were detectable in petunia corollas, styles, and ovaries. Expression patterns were not upregulated during petal senescence but were higher at the middle stages of development when flower corollas were fully open but not yet starting to wilt. PhMC1, a type I metacaspase previously identified in petunia, and PhMC2 were differentially regulated in vegetative tissues in response to biotic and abiotic stresses. PhMC2 expression was upregulated to a greater extent than PhMC1 following Botrytis cinerea infection, while PhMC1 was upregulated more by drought, salinity, and low nutrient stress. These results suggest that petunia metacaspases are involved in flower development, senescence, and stress responses.

• By endogenous PSKα signaling, sufficient intracellular ATP supplying supports flower bud opening. • Exogenous PSKα suppresses SnRK1 expression while triggers TOR expression. • Exogenous PSKα suppresses ProDH and IVDH expression while triggers AOX and UCP1 expression. • Exogenous PSKα suppresses endogenous H 2 O 2 accumulation. • Exogenous PSKα preserves membrane integrity revealed by lower electrolyte leakage and MDA accumulation. During bud opening of rose flowers, higher TOR along with lower SnRK1 expression was concomitant with sufficient cellular ATP provision, while during petal senescence of rose flowers, lower TOR along with higher SnRK1 expression was concomitant with insufficient cellular ATP supplying. During bud opening, higher TOR expression might ensure sufficient cellular ATP provision by promoting H+-ATPase, Ca2+-ATPase, SDH, and CCO activities. During petal senescence, higher SnRK1 expression might ensure for insufficient cellular ATP supplying which was associated with higher AOX, UCP1, ProDH and IVDH expression. By PSKα application, triggering TOR along with suppressing SnRK1 expression could be responsible for sufficient cellular ATP provision by promoting H+-ATPase, Ca2+-ATPase, SDH, and CCO activities accompanied by suppressing ProDH and IVDH expression. In addition, higher AOX and UCP1 expression might ensure lower H 2 O 2 accumulation in cut rose flowers by PSKα application. By PSKα application, retarding senescence and extending vase life of cut rose flowers was associated with maintaining membrane integrity indicated by lower electrolyte leakage and MDA accumulation. Our results suggest the potential of TOR/SnRK1 signaling pathways as an effective endogenous anti-senescence molecular mechanism for extending the vase life of cut rose flowers. [Display omitted] [ABSTRACT FROM AUTHOR]

Petal senescence affects the ornamental and economic value of carnation (Dianthus caryophyllus L.), one of the most important and typical ethylene sensitive cut flowers worldwide. Previous studies have revealed the molecular mechanisms of DcEIL3–1-DcWRKY75 transcriptional activation module and antagonistic competition between transcription factors DcWRKY75 and DcHB30 in regulating the expression of ethylene biosynthesis genes DcACS1 and DcACO1 and senescence associated genes DcSAG12 and DcSAG29 during ethylene induced petal senescence in carnation, but the regulatory mechanism among these three transcription factors is still unknown. Here, we investigated the transcriptional regulation network between these three transcription factors, and found that DcWRKY75 and DcHB30 can directly bind each other's promoter and inhibit each other's expression. Further, we found that DcEIL3–1 and DcHB30 also can directly bind each other's promoter and inhibit each other's expression. These findings further enrich our understanding about the molecular mechanism in regulating ethylene induced petal senescence in carnation, and also provide new strategies for postharvest preservation of cut carnation flowers. • DcWRKY75 and DcHB30 can directly bind each other's promoter and inhibit each other's expression. • DcEIL3-1 and DcHB30 can directly bind each other's promoter and inhibit each other's expression. • The transcriptional regulation network between DcEIL3-1, DcWRKY75 and DcHB30 may be conserved in other plants. [ABSTRACT FROM AUTHOR]

Flower senescence is classified into ethylene-dependent and ethylene-independent manners and determines the flower longevity which is valuable for ornamental plants. However, the manner of petal senescence in tulip is still less defined. In this study, we characterized the physiological indexes in the process of petal senescence, as well as metabolic and ethylene responses in tulip cultivar 'American Dream', and further identified the role of ethylene biosynthesis genes TgACS by transgenic and transient assays. Primary metabolites profiling revealed that sugars, amino acids and organic acids preferentially accumulated in senescent petals. Additionally, senescence-associated genes were identified and significantly up-regulated, coupled with increased ROS contents, rapid water loss and accelerated cell membrane breakdown. Moreover, ethylene production was stimulated as evidenced by increasing in ACS activity and ethylene biosynthesis-related genes expression. Exogenous treatment of cutting flowers with 1-MCP or ethephon resulted in delayed or enhanced petal senescence, respectively. Transient down-regulation of TgACS by VIGS assay in tulip petals delayed senescence, while over-expressed TgACS1 in tobacco promoted leaf senescence. Taken together, this study provides evidences to certify ethylene roles and TgACS functions during flower senescence in tulip. • Physiological responses of petal senescence in tulip are comprehensively analyzed. • Exogenous ethephon treatment promotes petal senescence in a dose-dependent manner. • Ethylene biosynthesis and primary metabolites modification are involved in petal senescence. • TgACS genes are functionally identified by transgenic tobacco plants and VIGS assay in tulip petals. [ABSTRACT FROM AUTHOR]

Highlights • The H 2 levels were decreased during senescence of lisianthus cut flowers. • Endogenous H 2 reduces the decay of cut flowers. • H 2 -induced delay of senescence requires the reestablishment of redox homeostasis. Abstract Exogenous hydrogen-rich water (HRW) improves vase life and quality of cut flowers, but the effects of endogenous hydrogen gas (H 2) are not known. During the vase of cut lisianthus flowers, endogenous H 2 concentrations decreased and redox homeostasis was impaired. The supplementation with HRW containing 0.078 mmol L−1 H 2 blocked, but 2,6-dichlorophenolindophenol (DCPIP; a putative inhibitor of H 2 synthesis) increased, endogenous H 2 production. Senescence of cut flowers was delayed by H 2 , but accelerated by DCPIP. Also, decreased vase life by DCPIP was blocked by H 2 administration. These beneficial roles of H 2 were associated with less lipid peroxidation, and the increased activities of superoxide dismutase, ascorbate peroxidase, guaiacol peroxidase, and catalase. Compared with DCPIP alone, the soluble protein, total chlorophyll, and proline contents were elevated when H 2 and DCPIP were added together. Overall, endogenous H 2 prolongs vase life of lisianthus cut flowers in part by maintaining redox homeostasis. [ABSTRACT FROM AUTHOR]

The Oncidium Gower Ramsey orchid is both an important cut flower plant and a potential good model plant for study the ethylene-sensitive floral senescence. Though significant progress has been made in understanding the physiological and molecular events occurred in petal senescence, little is known regarding the regulatory mechanism underlying onset of petal senescence. In this study, RNA sequencing and transcriptome analysis of petals during the transition from Oncidium flower opening to senescence were employed to identify novel regulatory genes and pathways in the initiation of ethylene-sensitive petal senescence. The petal senescence is a very active process accompanying differential expressions of a large number of genes. The key genes involved in the biosynthesis of gibberellin (GA), brassinosteroid (BR) and salicylic acid (SA), cytokinin (CK) homeostasis, CK and jasmonate (JA) signalling were found to be down-regulated in opening stage but up-regulated in senescent stage, and a gene in ethylene signalling was the reverse, suggesting that these hormones might play a role in the start of petal senescence. The transition-pattern expressions of major circadian clock genes showed that the timing of petal senescence might be under the circadian clock regulation. Moreover, epigenetic and transcriptional regulations were involved in the onset of petal senescence. [ABSTRACT FROM AUTHOR]

Ethylene plays a pivotal role in a wide range of developmental, physiological, and defense processes in plants. EIN2 (ETHYLENE INSENSITIVE2) is a key player in the ethylene signaling pathway. To characterize the role of EIN2 in processes, such as petal senescence, where it has been found to play important roles along with various other developmental and physiological processes, the tobacco (Nicotiana tabacum) ortholog of EIN2 (NtEIN2) was isolated and NtEIN2 silenced transgenic lines were generated using RNA interference (RNAi). Silencing of NtEIN2 compromised plant defense against pathogens. NtEIN2 silenced lines displayed significant delays in petal senescence, and pod maturation, and adversely affected pod and seed development. This study further dissected the petal senescence in ethylene insensitive lines, that displayed alteration in the pattern of petal senescence and floral organ abscission. Delay in petal senescence was possibly because of delayed aging processes within petal tissues. Possible crosstalk between EIN2 and AUXIN RESPONSE FACTOR 2 (ARF2) in regulating the petal senescence process was also investigated. Overall, these experiments indicated a crucial role for NtEIN2 in controlling diverse developmental and physiological processes, especially in petal senescence. • Silencing of EIN2 also has pleiotropic effects on pod maturation, pod size, seed yield, and plant defense in tobacco. • Reduced expression of EIN2 changes the pattern of petal senescence and almost abolishes floral organ abscission in tobacco. • Delayed petal senescence is possibly due to delayed cell death process. • EIN2-mediated ethylene signaling interacts with ARF2 (AUXIN RESPONSE FACTOR2)in regulating petal senescence [ABSTRACT FROM AUTHOR]

Early leaf yellowing in cut alstroemeria (Alstroemeria aurantiaca) flowers before flower development and petal abscission is an important limiting postharvest quality and vase life factors. Early leaf senescence reduces postharvest longevity of cut flowers and promotes petal's wilting. A study was made to evaluate the response of cut alstroemeria flowers at varying concentrations of cycloheximide (CHI) (50, 100 and 200 mg l-1), coconut water (5, 10 and 20%) and 6-benzyladenine (BA) (50, 100 and 200 mg l-1). CHI, coconut water and BA extended the vase life at all concentrations compared to the control, but coconut water at 5% concentration (with 17.39 days) was the most effective treatment. Control cut flowers showed the least vase life (10.76 days). Ethylene production in cut flowers promoted flower senescence. All concentrations of CHI, coconut water and BA delayed ethylene production compared to the control. Treatment of cut flowers with coconut water at concentration of 5% maintained the highest fresh weight of flowers and increased the content of water uptake. The chlorophyll degradation was significantly reduced by the application of CHI, coconut water and BA. The maximum content of membrane's lipid peroxidation and antioxidant enzymes activity (super oxide dismutase and peroxidase) was obtained in control cut flowers. Thus, 5% fresh coconut water has the potential to be applied as vase solution (preservative medium) due to prolongs of cut alstroemeria flowers.Â

A study was made to investigate differential responses of petal senescence and postharvest performance at varying concentrations of Cycloheximide (CHI) in cut spikes of Narcissus tazetta cv. Kashmir Local. Cycloheximide at 0.01 and 0.05 mM concentrations delayed senescence. Above 0.05 mM concentrations CHI prevents flower opening and promotes senescence. Senescence delay by CHI points to the synthesis of some specific proteins (enzymes) responsible for execution of cell death programme in flower petals. Cycloheximide at lower concentrations (0.01 and 0.05 mM) enhanced longevity, maintained a sustained rate of flower blooms, delayed senescence and optimized postharvest performance. Pulse treatment of spikes with CHI concentrations at 0.01 and 0.05 mM concentrations maintained high fresh and dry mass of flowers and lowered electrical conductivity of leachates. The content of sugars and proteins decreased, whereas that of α-amino acids and total phenolics increased in the petal tissues with CHI treatment; besides improving postharvest performance. Pretreatment of flowers with 0.01 or 0.05 mM CHI concentrations for 1 h enhanced vase life and improved postharvest performance in this flower system.

In flowering plants, floral longevity is species-specific and is closely linked to reproductive strategy; petal senescence, a type of programmed cell death (PCD), is a highly regulated developmental process. However, little is known about regulatory pathways for cell death in petal senescence, which is developmentally controlled in an age-dependent manner. Here, we show that a NAC transcription factor, designated EPHEMERAL1 (EPH1), positively regulates PCD during petal senescence in the ephemeral flowers of Japanese morning glory (Ipomoea nil). EPH1 expression is induced independently of ethylene signaling, and suppression of EPH1 resulted in Japanese morning glory flowers that are in bloom until the second day. The suppressed expression of EPH1 delays progression of PCD, possibly through suppression of the expression of PCD-related genes, including genes for plant caspase and autophagy in the petals. Our data further suggest that EPH1 is involved in the regulation of ethylene-accelerated petal senescence. In this study, we identified a key regulator of PCD in petal senescence, which will facilitate further elucidation of the regulatory network of petal senescence. [ABSTRACT FROM AUTHOR]

Summary To clarify whether climacteric-like increases in ethylene production of senescing petals are also induced in the absence of the gynoecium in cut carnation ( Dianthus caryophyllus cv. Barbara) flowers, we compared ethylene production and expression of ethylene-biosynthesis genes in detached petals and in petals, which remained on flowers (attached petals). No significant difference in longevity was observed between the attached and detached petals when held in distilled water, and both showed the inward rolling typical of senescing flowers. Treatment with silver thiosulfate complex (STS), an ethylene inhibitor, similarly delayed senescence of attached and detached petals. Climacteric-like increases in ethylene production of petals and gynoecium started on the same day, with similar bursts in attached and detached petals. Transcript levels of DcACS1 and DcACO1 were very low at harvest and increased similarly during senescence in both petal groups. Removal of the gynoecium did not significantly delay wilting of attached petals. In flowers with the gynoecium removed, the petals produced most of the ethylene while production by the other floral organs was very low, suggesting that wound-induced ethylene is not the reason for the ineffectiveness of gynoecium-removal in inhibiting flower senescence. These results indicate that ethylene biosynthesis is induced in carnation petals irrespective of the gynoecium. [ABSTRACT FROM AUTHOR]

Background: Pollination reduces flower longevity in many angiosperms by accelerating corolla senescence. This response requires hormone signaling between the floral organs and results in the degradation of macromolecules and organelles within the petals to allow for nutrient remobilization to developing seeds. To investigate early pollination-induced changes in petal gene expression, we utilized high-throughput sequencing to identify transcripts that were differentially expressed between corollas of pollinated Petunia × hybrida flowers and their unpollinated controls at 12, 18, and 24 hours after opening. Results: In total, close to 0.5 billion Illumina 101 bp reads were generated, de novo assembled, and annotated, resulting in an EST library of approximately 33 K genes. Over 4,700 unique, differentially expressed genes were identified using comparisons between the pollinated and unpollinated libraries followed by pairwise comparisons of pollinated libraries to unpollinated libraries from the same time point (i.e. 12-P/U, 18-P/U, and 24-P/U) in the Bioconductor R package DESeq2. Over 500 gene ontology terms were enriched. The response to auxin stimulus and response to 1-aminocyclopropane-1-carboxylic acid terms were enriched by 12 hours after pollination (hap). Using weighted gene correlation network analysis (WGCNA), three pollination-specific modules were identified. Module I had increased expression across pollinated corollas at 12, 18, and 24 h, and modules II and III had a peak of expression in pollinated corollas at 18 h. A total of 15 enriched KEGG pathways were identified. Many of the genes from these pathways were involved in metabolic processes or signaling. More than 300 differentially expressed transcription factors were identified. Conclusions: Gene expression changes in corollas were detected within 12 hap, well before fertilization and corolla wilting or ethylene evolution. Significant changes in gene expression occurred at 18 hap, including the up-regulation of autophagy and down-regulation of ribosomal genes and genes involved in carbon fixation. This transcriptomic database will greatly expand the genetic resources available in petunia. Additionally, it will guide future research aimed at identifying the best targets for increasing flower longevity by delaying corolla senescence. [ABSTRACT FROM AUTHOR]

Highlights: [•] Two indicators of programmed cell death, nuclear shrinkage and DNA fragmentation, were detected during flower senescence in the intact plant of Osmanthus fragrans. [•] Cut osmanthus flowers were sensitive to ethylene and petal abscission was mediated by ethylene. [•] Both ethylene and reactive oxygen species regulated DNA fragmentation. [•] Ethylene caused substantial damage to cellular structure. [Copyright &y& Elsevier]

Background: The petal senescence of ethylene insensitive species has not been investigated thoroughly while little is known about the temporal and tissue specific expression patterns of transcription factors (TFs) in this developmental process. Even less is known on flower senescence of the ornamental pot plant Gardenia jasminoides, a non climacteric flower with significant commercial value. Results: We initiated a de novo transcriptome study to investigate the petal senescence in four developmental stages of cut gardenia flowers considering that the visible symptoms of senescence appear within 4 days of flower opening. De novo assembly of transcriptome sequencing resulted in 102,263 contigs with mean length of 360 nucleotides that generated 57,503 unigenes. These were further clustered into 20,970 clusters and 36,533 singletons. The comparison of the consecutive developmental stages resulted in 180 common, differentially expressed unigenes. A large number of Simple Sequence Repeats were also identified comprising a large number of dinucleotides and trinucleotides. The prevailing families of differentially expressed TFs comprise the AP2/EREBP, WRKY and the bHLH. There are 81 differentially expressed TFs when the symptoms of flower senescence become visible with the most prevailing being the WRKY family with 19 unigenes. No other WRKY TFs had been identified up to now in petal senescence of ethylene insensitive species. A large number of differentially expressed genes were identified at the initiation of visible symptoms of senescence compared to the open flower stage indicating a significant shift in the expression profiles which might be coordinated by up-regulated and/or down-regulated TFs. The expression of 16 genes that belong to the TF families of WRKY, bHLH and the ethylene sensing pathway was validated using qRT – PCR. Conclusion: This de novo transcriptome analysis resulted in the identification of TFs with specific temporal expression patterns such as two WRKYs and one bHLH, which might play the role of senescence progression regulators. Further research is required to investigate their role in gardenia flowers in order to develop tools to delay petal senescence. [ABSTRACT FROM AUTHOR]

Summary: AtNAP, a NAC family transcription factor, has been shown to promote leaf senescence in Arabidopsis. We isolated an AtNAP homolog in morning glory (Ipomoea nil), designated InNAP, and investigated its expression during petal senescence. We used two cultivars, one showing a normal short flower life span (cv. Peking Tendan) and another a longer life span (cv. Violet). InNAP was highly expressed in both cultivars. Expression was high before that of the senescence marker gene InSAG12. InNAP and InSAG12 expression was high in cv. Peking Tendan before cv. Violet. The expression of both genes was therefore temporally related to the onset of the visible senescence symptoms. An inhibitor of ethylene action (silver thiosulphate, STS) delayed petal senescence in cv. Peking Tendan but had no effect in cv. Violet. STS treatment had no clear effect on the InNAP expression in petals of both cultivars, suggesting that endogenous ethylene may not be necessary for its induction. These data suggest the hypothesis that InNAP plays a role in petal senescence, independent of the role of endogenous ethylene. [ABSTRACT FROM AUTHOR]

Highlights: [•] A lily petal KDEL protease gene is transcriptionally up-regulated during senescence. [•] Westerns show post-translational processing in senescent petals. [•] Arabidopsis expressing the protease lacking the KDEL sequence senescence early. [•] The protein localises to the ER, but moves to the vacuole during senescence. [Copyright &y& Elsevier]